Melissa, we got a 7 month old doberman last fall who was on the thin side and had diahrea. He looked good at the check up though. We tried all kinds of dog food brands - very expensive brands, and the gas and diahrea stuck around. I finally looked up the bland food diet on the internet and switched his food to a homemade one. I cook up brown rice, burger (chicken would be better but expensive, so I make sure I drain all fat from the burger), sweet potatoes, mixed vegetables and mix in plain yogurt. His diahrea cleared up, the gas went away, and he gained weight. You can put your dog on this sort of diet for a couple of weeks and then try him again on regular dog food. I have found for my dog, though, that I couldn't put him back strictly on dog food or the problems come back. So I continue to make my homemade dog food and then mix in a small amount of good dry dog food to make sure he gets all the nutrients he needs. If I mix in too much dry, the gas comes back. If I keep the proportions right for him, no problems. But try switching your dog to a bland diet for a couple of weeks and see if that helps! Good luck!